1. Field of the Invention
The present invention is directed to a vibration damping device for a drive system of a motor vehicle having a base body arranged for rotating about an axis of rotation and a deflection mass arrangement arranged in the base body and having at least one deflection mass and a deflection path associated with the at least one deflection mass and along which the deflection mass is movable during rotation of the base body about the axis of rotation, the deflection path having a vertex area and deflection areas proceeding in opposite directions from the vertex area.
2. Description of the Related Art
A vibration damping device is disclosed in German reference DE 44 26 317 A1 having a plurality of deflection paths arranged in a base body and distributed about an axis of rotation of the base body. Deflection masses arranged in the base body are movable along these deflection paths which extend in the circumferential direction from vertex areas and curved toward the axis of rotation of the base body. During rotary operation of the base body, centrifugal forces arrange the deflection masses in respective vertex areas of the deflection paths, the vertex areas having the greatest radial distance from the axis of rotation. In the event of irregularities in the rotating speed, for example, as a result of rotational irregularities in an internal combustion engine drive, the deflection masses are deflected from their rest position in the vertex areas by these irregularities in rotational speed and move along their deflection paths in an oscillating manner. Higher harmonic orders of vibrational excitations in particular may be damped by so-called speed-adaptive dampers as described above. These dampers are adaptable to a specific vibration frequency to be damped through the selection of the radii of curvature of the curved paths and through the selection of the masses and dimensions of the respective deflection masses.
However, a problem with these prior art devices occurs when additional vibrational excitations occur, especially vibrational excitations of a different frequency or type. For example, when the above described vibration damper is used in a drivetrain in a motor vehicle between the crankshaft of an internal combustion engine and a transmission input shaft, an axial offset or axial inclination may be generated which forces the components of a clutch that are coupled together effect wobbling movements. Such wobbling movements also occur at certain frequencies and may impair the drive system.
It is the object of the present invention to further develop a vibration damping device that provides an improved damping function with respect to additional vibrational excitations.
The object is met according to a first embodiment of the present invention by a vibration damping device a motor vehicle drive system comprising a base body which is rotatable about an axis of rotation and deflection mass arrangement arranged in the base body and having at least one deflection mass and a deflection path associated with the at least one deflection mass and along which the deflection mass is movable during rotation of the base body about the axis of rotation. The deflection path has a vertex area and deflection areas proceeding in opposite directions from the vertex area.
The deflection areas proceed from the vertex area in substantially opposite axial directions. According to this embodiment, the deflection path extends substantially in the axial direction. The deflection area proceeding in the axial direction curves toward the axis of rotation of the base body. Therefore, the deflection mass moves substantially in a plane containing the axis of rotation. This movement of the deflection mass is substantially orthogonal to the movement direction of commonly known deflection masses and may be used to damp or eliminate wobbling excitations of the rotatable base body.
To further compensate for fluctuations in the rotational speed of the rotating system which are known per se and which originate, for example, from out-of-true running of an internal combustion engine, the deflection path associated with the at least one deflection mass has further deflection areas which proceed from the vertex area in substantially opposite circumferential directions.
In this embodiment, every deflection mass may accordingly move in an axial direction and in a circumferential direction, wherein an approach to or a distancing from the axis of rotation of the base body occurs in both the axial direction movements and the circumferential movements as a result of the curvature of the different paths. The deflection areas in the axial direction are connected with the additional deflection areas in the circumferential direction to form a deflection field for the associated deflection mass, wherein this deflection field faces the axis of rotation and is curved toward the axis of rotation. Accordingly, the at least one deflection body moves on a surface which is curved in three-dimensional space.
To arrange the movements such that they are as identical as possible in any direction, the at least one deflection mass forms a substantially spherical deflection body.
In a further embodiment of the present invention, the object of the invention is met by a vibration damping device for a motor vehicle drive system comprising a base body arranged for rotating about an axis of rotation and a deflection mass arrangement arranged in the base body having a plurality of deflection masses and a deflection path associated with every deflection mass and along which the deflection masses are movable during rotation of the base body about the axis of rotation.
This embodiment further comprises at least two deflection masses having a different mass and/or a different mass moment of inertia.
By providing different masses or mass moments of inertia in a plurality of deflection masses, each of these different deflection masses forms an oscillator with a different natural frequency. In this way, different excitations occurring in the rotating system at different frequencies may be simultaneously reduced.
This result may also be achieved by incorporating two differently configured deflection paths in addition to or instead of the two different masses or mass moments. The different paths may, for example, have a different curvature shape or have a different radial positioning with respect to the axis of rotation.
In an arrangement of this kind, the different deflection masses or deflection paths may be arranged so as to follow one another in the circumferential direction and/or arranged so as to follow one another in the axial direction depending on space considerations.
The above-stated object of adapting to very different frequency ratios is met according to another embodiment of the present invention in that at least one deflection path extends at least partly in a viscous damping medium. In addition, the natural frequency of the oscillator generated in this way may accordingly be influenced due to the fact that the deflection mass moving along the path must move in the medium and against increased resistance.
In this embodiment, a plurality of deflection paths may be arranged following one another in the circumferential direction. Each of the deflection paths defines a respective damping medium chamber and at least two of the damping medium chambers are connected with one another by a channel arrangement. In an arrangement of this type, the damping medium fluid may be displaced back and forth between the individual damping medium chambers. The back-and-forth displacement also has a determined natural frequency and therefore influences the oscillation behavior of the damper.
In this connection, the channel arrangement may open into the respective deflection paths defining the damping medium chamber.
Further, a channel arrangement may be arranged in the at least one deflection mass for the entrance of or passage of damping medium.
The viscous damping medium may comprise a damping fluid, for example. However, an easily displaceable material in powder form may alternatively be used for this purpose.
According to a further embodiment of the present invention, the above-stated object is met in that a friction arrangement is provided in damping devices of the type mentioned above for generating a frictional force opposing the movement of the at least one deflection mass.
The frictional force may be generated, for example, by the fluid or damping medium mentioned above. However, the friction arrangement may also comprise a pretensioning arrangement through which at least one deflection mass is pressed against an abutment arrangement.
With respect to construction, the friction arrangement may comprise a first wall area and a second wall area arranged at the base body, the at least one deflection mass being positioned between this first wall area and second wall area, and a pretensioning spring which acts between the at least one deflection mass and one of the first and second wall areas.
According to a further embodiment of the present invention, the object stated above is met in that the at least one deflection mass comprises a support bearing arrangement for supporting the deflection mass on the associated deflection path. In this way, the essential mass component of a deflection mass does not rotate even when rolling on the deflection path, since the rolling movement is received in the bearing arrangement. Accordingly, the energy introduced in the movement of the respective body is influenced in a defined manner. Only the kinetic energy of the movement along the path and no rotational energy is changed into the movement of the respective body.
For example, the support bearing arrangement may comprise a sliding bearing arrangement or a rolling body bearing arrangement.
The damping behavior of an oscillator of this kind may also be influenced in that the oscillating mass is compulsorily held in a determined position, i.e., can only execute a defined movement, and is stabilized in other directions. This especially prevents unwanted and undefined frictional contact with other components. According to another feature of the present invention, this result may be achieved in that the at least one deflection mass and the associated deflection path have a mutual contact profile such that the at least one deflection mass is stabilized in its position essentially in a plane containing the deflection path.
In this case, the at least one deflection mass may comprise an outer circumferential area with a substantially V-shaped surface profile. The associated deflection path also comprises a substantially complementary V-shaped path profile.
The vibration behavior may be further influenced in that the at least one deflection mass has at least one guide axle which is guided at a guide path at the base body or a component connected therewith, and in that the guide path for the at least one guide axle forms, at least partly, the deflection path for the associated deflection mass. The at least one guide axle proceeds from the deflection mass in this case and generates a rotation of the deflection mass when this guide axle rolls over the associated path. At a given deflection speed, that is, at a given movement speed of the body along the deflection path, the deflection body having a guide axle rotates at a substantially higher speed than a deflection body rolling on its outer circumferential surface. This result is exhibited because the guide axle has a smaller diameter than the deflection mass. As a result, a considerable proportion of rotational energy is changed in a defined manner into the moving deflection mass, which results in a corresponding damping or eradicating behavior.
For stabilizing the movement of the deflection mass, two oppositely arranged guide axles with associated guide paths may be arranged at the at least one deflection mass.
To rule out undefined friction losses as far as possible in this connection also, the at least one guide axle may be guided at the associated guide path with the intermediary of a bearing arrangement.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.